The objectives of this research is to establish if the unconjugated N-arylhyroxylamine and/or the nitroso derivatives of the bladder carcinogens nephthylamine, 4-biphenylamine and 2-fluorenylamine function as the proximal urinary and ultimate cellular carcinogens that induce tumor formation in the urinary bladder epithelium of the dog. Experimental evidence indicates that these N-oxidized metabolites interact with the DNA of the target tissue. Studies will be conducted to determine the nature and extent of these reactions with the DNA of the bladder epithelium and the possible role of the resulting modifications in the mechanism of the irreversible initiation to eventual malignancy of the target cells. We are engaged in the development of immunochemical methods that will have the necessary sensitivity and specificity for the study of these nucleic acid modifications induced in vivo in the urinary bladder epithelium by the exposure to the carcinogenic aromatic and their metabolic N-oxidation products.